Coded continuous inductive train control system



Oct. 4, 1938. w. H. REICHARD ET AL 2,131,752

CODED CONTINUOUS INDUCTIVE TRAIN CONTROL SYSTEM Filed Nov. 2'7, 1936 RedFIG. 2;

I Am U $413 15 J INVENTORS NHTeicrzard & (IS-Bushnell T 1 BY ZMQHM;

! THEIR ATTORN EY Patented Oct. 4, 1938 UNITED STATES PATENT OFFICECODED CONTINUOUS INDUCTIVE TRAIN CONTROL SYSTEM Application November 27,1936, Serial No. 112,858

9 Claims.

This invention relates to automatic train control systems for railroadsand more particularly to systems of the type commonly known as codedcontinuous inductive train control systems.

One object of the present invention is to provide a three indicationcontinuous inductive system of control whereby conditions in the fieldwill determine the presence of one of two train control currents ofdifferent frequencies in the track rails, and means whereby suchcurrents can be transmitted to a moving vehicle in a simple and directmanner to produce the various indications.

Another object of this invention is to provide, by arrangement andorganization of parts, means whereby car-carried apparatus is protectedagainst false indications due to the presence of stray currents in thetracks.

Other objects, advantages and characteristic features of this inventionwill be in part apparent and in part pointed out as the description ofthe invention progresses.

The trackway apparatus, in accordance with this invention, is such thatunder high speed running conditions, an alternating current of 140 cyclefrequency will be connected across the rails at one end of the tracksection, and under caution conditions a current of 90 cycle frequencywill be connected across the rails in a similar manner. The frequenciesof 90 and 140 cycles have been selected, because these frequencies'arehigher than the 25, 50 and 60 cycles ordinarily used for power andindustrial purposes, and thus avoid interference by these commercialfrequencies and their ordinary harmonics.

In describing the invention, reference will be made to the'accompanyingdrawing which shows. in a simple and diagrammatic manner, wayside andcar-carried apparatus constituting one spe- 40 cific embodiment of theinvention, the parts being shown in a manner to facilitate explanationand understanding of the essential characteristics of the invention, andnot necessarily to show the particular organization and constructionthat may be most advantageously used in practice. In the drawing:-

Fig. 1 is a diagrammatic view of one form of the invention.

Fig. 2 is a fragmentary diagrammatic view of parts in one operatingposition.

Fig. 3 is a fragmentary view of parts in another operating position.

The symbols and are employed to indicate the positive and negativeterminals, respectively, of suitable batteries or other sources ofelectrical energy, and those terminals with which these symbols are usedare presumed to have current flowing from the positive terminaldesignated to the negative terminal designated When these symbols areused in connection with alternating current circuits they are consideredto represent the instantaneous polarity of the respective terminals.

Referring to Fig. 1 of the accompanying drawing, asection of singletrack is shown with the track rails I divided into blocks by insulatedjoints 2, blocks C and D, and the adjacent ends of blocks B and E havingbeen shown. These blocks may be provided with block signals or thesesignals may be omitted and reliance placed on cab signals. Semaphoresignals S are shown conventionally without attempting to illustratetheir control circuits which may be of any well known type or form.

Suitable track relays T are connected across the track rails at theentrance end of each block, these relays being normally energized bytrack batteries 4 connected across the rails at the exit end of eachblock. Train control current is supplied to the rails of each block bytransformers 5, the secondaries of which are connected in series withthe track batteries '4 and their usual limiting resistances 6. Theprimary of transformer '5 of each block is connected to a source ofcurrent of either 140 or cycle frequency through front and back contact'1 respectively of the track relay T of the block next in advance.Therefore, it will be noted that current of 90 cycle frequency will beconnected across the rails at the exit end of the block next in the rearof an occupied block through back contact I of the track relay of theoccupied block, and current of cycle frequency will be connected acrossthe rails of the second block in the rear of the occupied block throughfront contact 7 of the track relay of the block next in advance, andlikewise for all blocks to the rear. The direction of current flow ineach of the track circuits has been indicated by the arrows a and a andis in opposite directions in the two rails. It is obvious that anyvehicle will always so shunt the track circuit that no train controlcurrent will be present in operating intensities behind, or in the rearof, a vehicle.

A locomotive or vehicle equipped with train control apparatus is shownconventionally in the drawing as comprising a pair of wheels and axle 8,which represent the first or leading pair of trucks of the vehicle.Carried ahead of the wheels and in inductive relation to the rails, are

receivers R and R of any usual construction. The voltages induced in thereceivers R and R by the flow of train control current in the trackrails, produce currents that are passed through band pass filters BPFand BPF of any usual construction, to the in-put side of suitableampliflers A and A of the vacuum tube or other type. These amplifiersare constructed in conformity with recognized principles to amplify thecurrents induced in receivers R and R by the train control currents inthe track rails. The band pass filters are designed to greatly attenuateany circulating stray currents of frequencies below cycles and abovecycles. Each receiver has its own filter and amplifying circuit and itsown out-put circuit connected to a poly-phase primary relay PR.

The relay PR is of the induction motor type, but is of specialconstruction and is provided with three sets of windings, one set ofwindings 9 corresponding to the local winding of a polyphase relay andenergized through a circuit which includes receiver R filter BPF andampli fier A Windings Ill and H are both connected to an out-puttransformer l2, of amplifier A, and are so tuned respectively, to 90 and140 frequencies that but one or the other winging receives current ofoperating intensity when current of one frequency is present in therails. In other words, and as shown in the accompanying drawing, windingII is tuned so that it is much more strongly energized than is windingID, by current of 140 cycle frequency, and winding I0 is tuned so thatit is much more strongly energized than is winding H, by 90 cyclecurrent. Thus in a block which is clear, or under high speed runningconditions, 140 cycle current is applied to the relay PR, and the energyin coils 9 and H produces a torque which operates the rotor of relay PRin a clockwise direction and closes contacts l3 and M to the left. In alike manner, when current of 90 cycle frequency, which corresponds to acaution condition, is present in the rails, current is applied to therelay PR and the energy in coils 9 and Ill produces a torque whichoperates the relay in a counterclockwise direction and closes contacts[3 and M to the right.

In order to produce operating torque in relay PR it is necessary thatthe time phase of the existing currents in windings 9 and ill, or 9 andIt of the relay should be displaced with respect to one another and tobe in quadrature or as close thereto as practical. A sufficient angulardisplacement of these field currents is produced by the adjustment ofthe separate amplifiers A and A Fig. 2 shows the position contacts l3and M will assume when relay PR is deenergized. Referring specificallyto contact l3 it is obvious that, with contact 13 biased to the positionshown coils l0 and H are both connected to a secondary coil oftransformer l2 but the direction of rotation of relay PR will bedetermined only by the coil tuned to receive the particular frequencyapplied.

With contact 13 positioned as shown in Fig. 2, a movement of the contactfinger through an arc of approximately 10 either to the right or left issufficient to break the right and left-hand contacts respectively. Amovement of contact finger l4 through an arc of approximately 45 isnecessary to close either its right or left-hand contacts.

Fig. 3 shows theposition of contacts l3 and l4 after relay PR is movedto its right-hand position the result of a current of 90 cycle frequencybeing applied to the coils of the relay.

The relay PR may be employed to control any suitable or desired form ofautomatic train control indicating apparatus, which is controlled bythree influences or controls corresponding to said relay beingdeenergized or energized to a clockwise or counterclockwise position.One suitable form of such application is shown in the drawing, it beingunderstood that this application could be amplified so as to includeacknowledging contactors and audible indications, etc, if desired,without departing from the scope of the invention, such, for example, asshown in Patent No. 1,703,831, issued February 26, 1929, to W. H.Reichard.

Assuming block E to be occupied, as shown, by a vehicle V, when vehicle8 is in a clear or green block, as C, or B, as shown, alternatingcurrent p.

of I40 cycle frequency is applied to the rails through front contact Iof a track relay T and transformer 5. The currents induced in receiversR and R are applied to relay PR to cause relay PR to operate in aclockwise'direction and close contacts l3 and M to the left. Thisenergizes the green indication G in the cab, through a circuit tracedfrom positive battery, contact I l in its left-hand position, greenlight G, to negative battery.

If vehicle 8 enters track section D, 90 cycle current, supplied to therails through a transformer 5 and back contact 1 of a track relay T willcause relay PR to operate in a counterclockwise direction and closecontacts l3 and I4 to the right. The green indication G will beextinguished and the yellow indication Y will then be displayed in thecab through a circuit which may be traced from positive battery, contactM to the right, the yellow indication light Y, to negative battery.

If vehicle 8 moves into the occupied track section E, relay PR willassume its deenergized position as no appreciable energy is present inthe rail to the rear of V. Contacts 13 and I4 will then assume theirenergized neutral biased position and the red indication R will bedisplayed in the cab through a circuit obvious from the drawing. 1

One of the important features of this invention is the protectionafforded against false operation of relay PR by stray currents in therails of a frequency the same as, or close to, the regular train controlcurrent. Such stray currents may be falsely applied from a transmissionline due to crosses, grounds and the like, or may come from some foreignsource, of a frequency so like the train control frequencies that theband pass filters and the amplifiers are not sufficient to avoidoperation of relay PR for large values of stray current. Such straycurrents ordinarily flow in one rail alone or in both rails equally orunequally but in the same direction for any given instant.

The application of the amplifiers A and A in connection withtheoperation of relay PR can guarantee operation only from currentswhich are derived from an inter-rail potential, and when the currentflows down one rail to the shunting axles of the vehicle, and back tothe source over the other rail. This is the case for the reason that thecoils are so arranged that the instantaneous polarities of the currentsin these coils are such that eifective operating torque is available inrelay PR only'when the iii] currents in the track circuit flow inopposite directions i. e.,.in a loop circuit.

If a condition be assumed in which the vehicle carrying train controlequipment is in a danger or red block, and a current of train controlfrequency is flowing in one rail only, it is evident thatrelay PR willnot operate as only one of its coils is energized.

If, however, under the same conditions, currents of operating frequencywere present in both rails and in the same direction, (i. e. simplexcurrent in the rails) the instantaneous relative polarity of one of thereceivers is reversed, with respect to the other. Ordinarily this wouldproduce an operating reverse torque in the out-put circuit, and in theordinary polyphase induction motor-type relay reverse operation wouldtake place. In order to prevent such operation it will be noted that thecircuit to winding II which normally produced clockwise torque, (i. e.,with loop current in the rails) is'broken through contact 13 of relayPR, which opens when the relay moves in a counterclockwise direction.Also the circuit for winding 10, which produces counterclockwise torquewith loop current in the rails, is broken when the relay is moved in aclockwise direction. Therefore, it is clear, that if the relay shouldtend to operate, due to stray circulating currents which flow in thesame direction in both rails, the response of the relay to such acondition will be in a direction to interrupt or disconnect theoperating field which produced such an initial movement.

If a condition be assumed in which vehicle 8 is in a yellow or cautionblock and a stray current of 140 cycle frequency corresponding to aclear block, is present in the same direction in both rails, the stray,current will have no effect on relay PR as the circuit to coil II isopened as indicated by the position of contact 13 in Fig. 3. Thepresence of astray current of cycle frequency will not effect theoperation of relay PR when the vehicle carrying train control apparatusis in a green block ascontact I3, as shown in Fig. 1, will open thecircuit to coil II].

If vehicle '8 enters either a green or yellow block in which the straycurrent in both rails is of the same frequency as the train controlfrequencies, relay PR in each case will have a tendency to operate in areverse direction. However, the circuit that supplies the energy forthis reverse operation will be interrupted as heretofore described bythe operation of contact l3. As a result, if, for example, when vehicle8 is in a green block and a stray current of cycle frequency appears inboth rails, contact l3 of relay PR will move from its position, as shownin Fig. 1, to a position slightly to the right of that shown in Fig. 2,at which point the left-hand contact I3 will be open. The relay willthen operate to intermittently close and open contact l3 but the signalcontrol contact I4 will not move through a sufficient arc from itsposition shown in Fig. '3, to close its righthand contact. Thus, in thecircumstances assumed, a flashing redindication will be displayed in thevehicle after the green indication has been extinguished. Likewise, ifvehicle 8 is in a cautionor yellow block and a stray current of 90 cyclefrequency appears in both rails, relay PR will operate in a mannersimilar to that described above, i. e., in a manner that will result ina flashing red indication being displayed in the car after the yellowindication has been extinguished.

The above rather specific description of one form of system embodyingthe present invention, has been given solely byway of illustration, andis not intended, in any manner whatsoever, in a limiting sense.Obviously, the invention can assume many different physical forms, andis susceptible of numerousmodifications, and all such forms andmodifications are desired to be included by this invention, as comewithin the scope of the appended claims.

Having described our invention, we claim:

1. In a train control system, in combination, trackway apparatus forplacing current of two different frequencies on the rails in a loopcircuit, in accordance with traflic conditions ahead, car-carriedapparatus, including two receivers energized by the track rail currentsof either frequency, a three-position relay of the induction motor typehaving a local winding and a normal and a reverse winding, a circuitincluding the local winding and one receiver, and a circuit connectingthe other two windings to the other receiver, and means tuning thenormal winding for one of the frequencies of rail current, and thereverse winding for the other frequency of rail current whereby therelay is energized to one or the other of its extreme positions inaccordance with the frequency of rail current in the rails, meansbiasing the relay to a central position, and three condition indicatingmeans distinctively controlled by the relay.

2. In a train control system, in combination, trackway apparatus forplacing current of either of two different frequencies on the rails in aloop circuit, in accordance with traffic conditions ahead, car-carriedapparatus, including two receivers energized by the track rail currentsof either frequency, a three-position relay of the induction motor typehaving a local winding and a normal and a reverse winding, a circuitincluding the local winding and one receiver, and a circuit connectingthe other two windings to the other receiver, and means tuning thenormal winding for one of the frequencies of rail current, and thereverse winding for the other frequency of rail current whereby therelay is ener gized to one or the other of its extreme positions inaccordance with the frequency of rail current in the rails, meansbiasing the relay to a central position, and three condition indicatingmeans distinctively controlled by the relay contact control.

3. In a train control system of the continuous inductive type,car-carried apparatus including a relay having a local winding, a normalwinding, and a reverse winding, means responsive to rail current forapplying current of one character, or another character to the windingsof the relay, means permitting the local winding and one only of theother windings to be energized at any one time dependent upon thecharacter of the current applied; the relay being operated to itsnormal, or reverse, position upon its normal, or reverse winding beingthus energized.

4. In a train control system of the continuous inductive type,car-carried apparatus including a relay having a local winding, a normalwinding, and a reverse winding, means responsive to rail current forapplying current of two different frequencies to the windings of therelay, and the normal and reverse windings being tuned, respectively, toone, and the other, of such different frequencies, the relay beingoperated to its normal, or reverse position upon its normal or reversewinding being thus energized.

5. In a train control system of the continuous inductive type,car-carried apparatus including a relay having a local winding, a normalwinding, and a reverse winding, means responsive to rail current forapplying current of one character, or another character to the windingof the relay, means permitting the local winding and one only of theother windings to be energized at any one time dependent upon thecharacter of the current applied; the relay being operated to itsnormal, or reverse, position upon its normal, or reverse winding beingthus energized, a winding control contact on the relay, means biasingthe contact to a central position Where it closes an energizing circuitfor both normal and reverse windings, said contact opening the circuitfor either the normal, or the reverse, winding upon movement of therelay a short distance from its biased neutral position.

6. In a train control system of the continuous inductive type,car-carried apparatus including a relay having a local winding, a normalwinding, and a reverse winding, means responsive to rail current forapplying current of one character, or another character to the windingof the relay, means permitting the local winding and one only of theother windings to be energized at any one time dependent upon thecharacter of the current applied; the relay being operated to itsnormal, or reverse, position upon its normal, or reverse winding beingthus energized, a winding control contact on the relay, means biasingthe contact to a central position where it closes an energizing circuitfor both normal and reverse windings, said contact opening the circuitfor either the normal, or the reverse, winding upon movement of therelay a short distance from its biased neutral position, the currentsbeing of different frequencies, and the normal and reverse windingsbeing tuned, respectively, to one, and the other, of such differentfrequencies.

7. In a train control system of the continuous inductive type, incombination, trackway apparatus with means for placing one of twofrequencies on the track rails in a loop circuit, in accordance withtraffic conditions ahead, carcarried receiving apparatus, including tworeceivers energized by track rail currents of either frequency, athree-position relay of the inductive motor type having a local windingand a normal and a reverse Winding, a circuit including the localwinding and one receiver, and a circuit connecting the other twowindings to the other receiver by means of a winding control contact,means tuning the normal Winding for one fre quency of rail current, andthe reverse winding for the other frequency of rail current, the relaybeing energized to one on the other of its extreme positions inaccordance with the frequency of the loop circuit current in the trackrails, and means biasing the relay to neutral position with no loopcurrent in the rails, to display the most restrictive indication, andmeans whereby said winding control contact operates to break the circuitto either the normal or the reverse winding when the relay responds to asimplex rail current of either said one, or said other, frequencyrespectively, to display the most restrictive indication.

8. In a train control system, in combination,

trackway apparatus for placing any one of a plurality of currents, offrequency determined in accordance with traffic conditions ahead, on therails in a loop circuit, whereby the current in the rails, at any giveninstant flows in opposite directions in the two rails, separatecar-carried receiving means with one over each rail for receiving theenergy of said rail currents of different frequencies, decoding means onthe car including a primary translating means connected to one of thereceiving means and a plurality of other translating means connected tothe other receiving means and each arranged in quadrature to the saidprimary translating means, whereby to be distinctively responsive toenergy of each of said currents of different frequencies, and to thephase relation of the two currents in the said separate receiving meansto assume distinctive positions, a plurality of indicators of varyingrestrictivenesses controlled by the decoding means in its distinctivepositions to thereby set up indications varying in restrictiveness, amost restrictive indicator, means biasing the decoding means to aposition to control the most restrictive indicator to give a mostrestrictive indication, control contacts for said plurality of. othertranslating means, said decoding means responding to rail currentflowing through the rails in the same direction at any given instant, orin one rail only, and of any frequency, to move said control contacts soas to cause the display of the most restrictive indication.

9. In a train control system, in combination, trackway apparatus forplacing either one of two currents, of one or the other of two differentfrequencies as determined by traffic conditions ahead, on the rails in aloop circuit, whereby the current in the rails, at any given instantflows in opposite directions in the two rails, separate car-carriedreceiving means with one over each rail for receiving the energy of saidrail currents of diiferent frequencies, decoding means on the carincluding a primary translating means connected to one of the receivingmeans and a plurality of other translating means connected to the otherreceiving means and each arranged in quadrature to the said primarytranslating means, whereby to be distinctively responsive to energy ofeach of said currents of different frequencies, and to the phaserelation of the two currents in the said separate receiving means toassume distinctive positions, a plurality of indicators for indicatingclear, caution and danger and controlled by the decoding means in itsdistinctive positions to thereby set up corresponding indications, meansbiasing the decoding means to a position to control the danger indicatorto give a danger indication, control contacts for said plurality ofother translating means for setting up clear and caution indications inresponse, respectively, to energy of one of said frequencies, and toenergy of the other of said frequencies, said decoding means respondingto rail current flowing through the rails in the same direction at anygiven instant, or in one rail only, to cause the display of the dangerindication.

WADE H. REICHARD. CHARLES S. BUSHNELL.

